In recent years olefin polymers have found extensive use in the preparation of a wide variety of products such as fibers, bottles, films, etc. It is well known that exposure to sunlight or other sources of ultraviolet light cause the degradation of olefin polymers. Such degradation is shown by a loss in the molecular weight of the polymer, by the development of color, and by a decrease in such physical properties as tensile strength to the point of mechanical failure. This type of degradation has in the past been dealt with by the incorporation in the polymer composition of certain additives which are effective to inhibit it.
Certain organic nickel complexes are known to be effective ultraviolet stabilizing agents because, it is believed, they tend to inactivate excited molecular species which otherwise would cause chain scission and degradation of the polymer molecule.
In general, nickel compounds exist as one of three geometric configurations, square planar, tetrahedral (where nickel has a coordination number of 4), or octahedral (where nickel has a coordination number of 6). The latter is the most common. The organic nickel complexes here are believed to have a tetrahedral structure inasmuch as they are derivable from nickel carbonyl which is known to have a tetrahedral structure.
U.S. Pat. No. 3,661,843 (Hechenbleikner et al.), for example, shows the utilization as stabilizers of organic solid polymer materials of a wide variety of organic nickel complexes which contain phosphorus. One of the organic nickel complexes shown, at column 16, lines 8-13, is characterized by the structural formula ##STR1## It apparently was prepared by the reaction of nickel carbonyl and pentaerythritol phosphite.
U.S. Pat. No. 3,959,220 (Hechenbleikner et al.) and U.S. Pat. No. 4,012,399 (Hechenbleikner et al.) have the same disclosure as that of the above Hechenbleikner et al. patent.
U.S. Pat. No. 4,276,195 shows the reaction of a normally homogeneous transition metal catalyst, such as tetrakis trimethylphosphite nickel(0), with a polydentate ligand such as dimethyl pentaerythritol diphosphite. The product is a polymeric solid which is an effective catalyst in the isomerization of olefins.